1. Field of the Invention
This invention relates to a surface-emitting laser (SEL) device, more particularly to a surface-emitting laser (SEL) device including a two-dimensional photonic crystal (2DPC) having optical nanostructures extending through a multi-quantum well (MQW) and a normalized frequency ranging from 0.25 to 0.7.
2. Description of the Related Art
A conventional vertical cavity surface-emitting laser (VCSEL) device includes an active region, which is capable of generating photons therein, and a pair of distributed Bragg reflectors (DBRs) sandwiching the active region therebetween so as to permit the photons to resonate between the upper and lower DBRs such that the photons can be stimulated to gain sufficient power in order to be able to be emitted to the outside along the vertical direction. However, each of the DBRs is composed of a plurality of alternately disposed high and low refractive index layers, which can cause the conventional VCSEL to emit a laser light with multiple transverse modes, which, in turn, can result in a decrease in the output power of the conventional VCSEL.
Referring to FIG. 1, U.S. Pat. No. 6,704,343 B2 discloses a conventional high power single mode vertical cavity surface-emitting laser (VCSEL) device 100 including a substrate 108, a plurality of DBR layers 106 formed on the substrate 108, an active region 104 formed on the DBR layers 106 for generating photons, and a two-dimensional photonic crystal (2DPC) 102 formed on the active region 104 and having a cavity structure composed of cavities 101, 103, and 105. The two-dimensional photonic crystal (2DPC) 102 is effective to reflect the photons having a specific wavelength and moving in the vertical direction. As a consequence, the photons with the specific wavelength can be resonated between the 2DPC 102 and the DBR layers 106 so as to gain sufficient power to generate a high power laser light with a single mode, i.e., a single wavelength. Although the VCSEL 100 can emit high power laser light, formation of a large number of the DBR layers 106 can result in a considerable increase in the manufacturing costs and time.